Chevrolet Silverado 2014 Z71 - Acceleration Buzz

[sanforce]

Hello GM-Trucks, I have a question that I cannot get to the bottom of, and was wondering if any of you could help.

 

My Chevrolet Silverado 2014 Z71 produces a weird buzz when accelerating. The truck has aftermarket exhaust, but the sound showed up long after the exhaust was installed. The buzz sound is not present while the engine is idling, but is present in drive, reverse, or park when the accelerator is pressed. The sound originates from somewhere inside of the front left tire, but I cannot pinpoint the location. Also, the sound is not present every time I use the truck. But, it's getting really obnoxious to me and I'd really like to determine the source to get it fixed.

 

I went to my normal Chevrolet dealership shop, and they were no help. They were very eager to provide my next scheduled service (60,000 miles) around 10,000 miles early, but seemed irritated when I brought up this "unknown" problem. I took the service manager over to my truck and had him listen to the sound, and he said that it all sounds fine and this buzz is a normal sound for these trucks... but there is NO WAY this is a normal sound. It showed up after driving on dirt roads the past summer. The service manager basically said they could take a look while performing the 60,000 mile service, but couldn't guarantee anything. I wasn't satisfied with their answer and might never use that shop again because of it.

 

Here is a video of the buzz sound, filmed underneath the driver door: 

 

Anyone have any idea what this could be?!